This invention relates to a wear-limit warning device for use in a vehicle disc brake, which warns the driver that a permissible wear limit of the friction pads has been reached, for informing of the necessity of replacing the worn-out pads.
Friction pads of a disc brake are each provided with a friction member disposed facing the friction surface of the disc rotor, and a backing plate secured to the rear surface of the friction member. The friction pads are pressed against the disc rotor upon actuation of the brake by an actuator thereby restraining rotational movements of the rotor, and are supported by a torque member so that they are movable along the axis of the rotor. The friction pads whose friction members are worn during service are required to be replaced when the amount of wear of the friction members has reached their permissible limit. For this reason, there have been proposed various wear-limit warning devices which inform the vehicle driver that the permissible wear limit of the friction member has been reached. Some novel wear limit devices were also developed by the inventors of the present invention, for which a U.S. Pat. No. 343,476 was filed on January 28, 1982. Those devices are characterized by the use of a warning member made from a sheet material which comprises: a mounting leg portion which is fixed to the sidewise end portion of the backing plate of the friction pad; a contact portion extending along the sidewise end face of the backing plate, with its free end reaching a wear limit level; and a spring portion connecting the mounting leg and contact portions in a space behind the rear surface of the backing plate, and producing a resilient force with which the contact portion is pressed against the sidewise end face of the backing plate or the mounting leg portion. When the wear limit of the friction member has been reached, the free end of the contact portion comes into contact with the rotating disc rotor and generates an extremely clear warning sound.